An environment in which the instant inventive electric conductivity water probe may be advantageously used is an airport aircraft maintenance tarmac. In such environment, a fuel truck having a tank for transporting aircraft fuel commonly services aircrafts by pumping fuel into an aircraft's fuel tanks. Water, which upon occasion undesirably collects within and contaminates the tank of such a fuel truck, is necessarily prevented from being pumped into the aircraft's fuel tanks.
A common means for preventing water contaminated fuel from being pumped into an aircraft's fuel tanks is to interpose a water separating vessel or tank in line with a fuel transmission line extending between such truck and such aircraft. Such vessel commonly encases a first stage water coalescing element and a second stage water separating element, and has a fuel inlet port, a fuel outlet port, a low end water collecting sump, and a purging port for draining water from the sump.
In normal operation of such water separating vessels, only small amounts of water are expected to be separated from fuel which is pumped therethrough during a single aircraft refueling process. Such small volume of water is conveniently purged immediately following each aircraft fueling operation. However, on occasion, an excessive amount of water may be present within a fuel truck's tank, resulting in transmission of an excessive amounts of water to the water separating vessel. In the event water within the sump of such water separating vessel rises to a level at which portions of the vessel's coalescing and separating elements are submerged in water, the vessel's ability to further separate water from fuel may become compromised. Such a malfunction of the water separator potentially allows water laden fuel to be pumped into an aircraft's fuel tanks. In-flight aircraft engine failure and a catastrophic crash can result when the engine ingests water contaminated fuel.
In order to provide a safeguard against pumping water laden aircraft fuel downstream from a water separating vessel, means for detecting dangerously high water accumulations within such water separating vessels are commonly provided, such means operatively triggering, for example, a fuel truck pump motor “kill” switch. Electric conductivity water probes are a preferred means for detecting high water levels within such water separating vessels. Such probes desirably eliminate mechanical moving parts and avoid requirements of maintaining narrow buoyancy parameters which are inherent in fuel/water mechanical float switches.
Where an electric conductivity probe is utilized as a high water level testing means within such water separating vessel, the electrode or electric circuit completion point of such probe is typically mounted within or upon a wall of such water separating vessel in an orientation wherein the electrode is normally bathed and non-electrically conductive aircraft fuel. Under normal operating conditions, in the event that electrically conductive water rises within such water separating vessel to the level of such electrode, the aircraft fuel is washed away from the electrode by the water, and the water immediately completes an electric circuit which is communicated electrically for operation of, for example, a pump motor kill switch. However, aircraft fuel pumped through the water separator vessel may, on occasion, be further contaminated (over and above water contamination) by electrically insulating substances which tend to coat the electrode, acting as an electrical insulator. Where such electrode coating contaminants are present, excess water within the water separating vessel will not necessarily complete an electric circuit within the water probe. In such event, the aforementioned exemplary pump motor kill switch may not be actuated in response to an excess water event, and water laden fuel may be undesirably pumped downstream and into an aircraft's fuel tank.
A method for protecting against foreign matter deposit induced electric conductivity water probe failure is to shut down and disassemble the water separating vessel, exposing the interior electrical contact point or electrode to visual inspection. However, such measures are mechanically complex and time consuming, resulting in an undesirable aircraft refueling system down time.
Another known method of protecting against such foreign matter deposit induced electric conductivity water probe failure is to purposefully create high water conditions within the water separating vessel, and to observe the function of the water probe during the known high water event. However, such protective procedures similarly are time consuming, and undesirably result in aircraft fueling system down time.
The instant inventive electric conductivity water probe solves or ameliorates all of the problems set forth above by providing an electric conductivity water probe which is capable of normally functioning as a water test probe and which is further capable of alternately performing a function of “mimicking” a high water event within a water separating vessel without requiring the occurrence of an actual high water event.